Abstract

Background

Saccharide materials have been used for centuries as binding media, to paint, write
and illuminate manuscripts and to apply metallic leaf decorations. Although the technical
literature often reports on the use of plant gums as binders, actually several other
saccharide materials can be encountered in paint samples, not only as major binders,
but also as additives. In the literature, there are a variety of analytical procedures
that utilize GC-MS to characterize saccharide materials in paint samples, however
the chromatographic profiles are often extremely different and it is impossible to
compare them and reliably identify the paint binder.

Results

This paper presents a comparison between two different analytical procedures based
on GC-MS for the analysis of saccharide materials in works-of-art. The research presented
here evaluates the influence of the analytical procedure used, and how it impacts
the sugar profiles obtained from the analysis of paint samples that contain saccharide
materials. The procedures have been developed, optimised and systematically used to
characterise plant gums at the Getty Conservation Institute in Los Angeles, USA (GCI)
and the Department of Chemistry and Industrial Chemistry of the University of Pisa,
Italy (DCCI). The main steps of the analytical procedures and their optimisation are
discussed.

Conclusions

The results presented highlight that the two methods give comparable sugar profiles,
whether the samples analysed are simple raw materials, pigmented and unpigmented paint
replicas, or paint samples collected from hundreds of centuries old polychrome art
objects. A common database of sugar profiles of reference materials commonly found
in paint samples was thus compiled. The database presents data also from those materials
that only contain a minor saccharide fraction. This database highlights how many sources
of saccharides can be found in a paint sample, representing an important step forward
in the problem of identifying polysaccharide binders in paint samples.